The invention relates generally to methods for retrofitting existing work vehicles for improved performance. More particularly, it relates to method for retrofitting the hydraulic system of a backhoe with a swing damping circuit for damping the unwanted oscillation of the backhoe assembly.
Backhoes and other work vehicles have jointed arms that pivot about a vertical axis to position a tool, typically a bucket or similar excavation device. These vehicles are typically engaged in repetitive movement, from side-to-side, picking up a bucket of soil, for example, pivoting to the side, and dumping the bucket of soil, only to return to their original location and begin the process again.
One of the continuing weaknesses of these vehicles is their inability to rapidly position the arm, and hence the bucket, in position over the digging site. When the arm is pivoted and stopped, the sudden closing of the directional control valve that controls flow to and from the boom swing cylinder causes the arm to oscillate side-to-side for some seconds before coming to a complete stop. This oscillation causes delay. Each cycle of scooping and dumping includes the time required to wait for the bucket to stop oscillating.
Co-pending U.S. patent application Ser. No. 09/661,348, describes a circuit that stops this oscillation when attached to a backhoe or other device. Generally speaking, the circuit connects the two hydraulic lines that extend from the directional control valve to the actuator or actuators that actually cause the boom to swing side-to-side. The circuit senses the deceleration of the backhoe arm based upon the various pressures and fluid flows through the two hydraulic lines, then opens a bypass passageway between the two hydraulic lines to permit fluid to flow from one line to the other. Hydraulic fluid is thereby permitted to escape a high-pressure port of the hydraulic actuator and be conducted to a low-pressure port of the hydraulic actuator.
It has been discovered that this circuit (called a xe2x80x9cswing-damping circuitxe2x80x9d) can increase the productivity of a backhoe by as much as 20%. In other words, by reducing unwanted oscillation of the backhoe arm and the inherent delay while the oscillation stops, a backhoe operator may increase the amount of material that can be moved by 20%. It would therefore be beneficial to provide this capability for currently existing backhoes. What is needed, therefore, is a method for retrofitting a backhoe, backhoe valve assembly or boom swing valve with a boom swing damping circuit. It is an object of this invention to provide such a method.
In accordance with the first embodiment of the invention, a method of retrofitting a boom swing control valve with a backhoe assembly swing damping circuit is provided includes the steps of disconnecting a pair of hydraulic lines from the output ports of the boom swing control valve, coupling the swing damping circuit to the boom swing control valve, and connecting a pair of hydraulic lines to the output ports of the swing damping circuit. The step of coupling may include the step of attaching the first valve body having the swing damping circuit to a second valve body having the boom swing control valve. The step of attaching may include the step of bolting the first valve body to the second valve body. The step of bolting may include the step of inserting a bolt through a portion of the first valve body and threading the bolt into the second valve body. The first valve body may define first and second ports configured to receive fluid from and transmit fluid to the second valve body. The second valve body may define third and fourth ports configured to receive fluid from and transmit fluid to the first valve body. The step of attaching may include the step of aligning the first port with the third port and aligning the second port with the fourth port. The step of attaching may include the step of abutting the first and third port and abutting the second and the fourth port. The step of attaching may include the step of fixing the first valve body to the second valve body after the steps of aligning and abutting.
In accordance with the second embodiment of the invention, a method for retrofitting a backhoe with a boom swing damping circuit is provided where the backhoe includes a vehicle, a backhoe assembly pivotally coupled to the vehicle, a swing cylinder coupled to the vehicle and to the backhoe assembly to pivot the backhoe assembly, an operator actuated boom swing control valve with a first port coupled via a hydraulic line to a port of the swing cylinder and a second port also coupled via a second hydraulic line to the swing cylinder, wherein the swing damping circuit includes a valve body defining a first fluid path that extends between the first inlet and outlet port in the valve body and a second path extending between a second and inlet and outlet port of the valve body and defining a third fluid path that fluidly couples the first and second paths and also includes a bypass valve in the third path to control fluid flow through the third path where the method includes the steps of disconnecting the first and second hydraulic lines from the first and second outlet ports of the boom swing control valve aligning the inlet ports of the valve body of the swing damping circuit with the outlet ports of the boom swing control valve and coupling the first and second inlet ports of the valve body of the swing damping circuit to the first and second outlet ports of the control valve. The inlet ports of the valve body the swing damping circuit may be formed in a first generally plainer surface of the swing damping circuit valve body. The first and second outlet ports of the control valve may be formed in a second generally plainer surface of the control valve body. The step of aligning may include the step of positioning the first and second surfaces into an abutting relationship.
In accordance with the third embodiment of the invention, a method for retrofitting a backhoe with a boom swing damping circuit is provided where the backhoe has a boom swing control valve that""s fluidly coupled to at least one boom swing cylinder by first and second hydraulic lines and the method includes the steps of disconnecting the boom swing control valve from the boom swing cylinder, fluidly coupling the two hydraulic lines to a swing damping circuit with a bypass valve disposed in the swing damping circuit to conduct fluid between the first and second hydraulic lines and reconnecting the boom swing control valve to the boom swing cylinder. Swing damping circuit may include first and second flow restrictors, these flow restrictors may be disposed to restrict flow between the boom swing control valve and the boom swing cylinder after the step of reconnecting.
In accordance with a fourth embodiment of the invention, a method of retrofitting a backhoe valve assembly with a swing damping circuit is provided where the valve assembly has a boom swing valve section, a boom lift valve section, a dipper lift valve section, each fluidly coupled by two hydraulic lines to a corresponding hydraulic cylinder for swinging the boom, lifting the boom and lifting the dipper, where the method includes the steps of removing the boom swing valve section from the valve assembly and replacing the boom swing valve section in the valve assembly with a combination boom swing valve and swing damping circuit section where the combination valve section includes a valve spool responsive to operator actuation and configured to provide bi-directional flow to the boom swing cylinder through two hydraulic lines and the swing damping circuit that responds to deceleration of a backhoe assembly and includes a bypass valve configured to provide fluid flow path that couples the extend port to the retract port of the boom swing cylinder. Method may include the step of combining the boom swing valve section with a swing damping circuit to create the combination valve section. It may also include the step of disconnecting the boom swing valve section from corresponding first and second hydraulic lines. It may also include the step of fluidly coupling the combined valve section to extend and retract ports of the boom swing cylinder. The method may also include the step of fluidly coupling the first hydraulic line to first outlet port of the combined valve section and to the extend port of the boom swing cylinder and fluidly coupling another hydraulic line to a second outlet port of the combined valve section and to a retract port of the boom swing cylinder. The bypass valve may include a fluid pressure actuated spool where the combined valve section includes a unitary valve body housing both an operator actuated directional control valve spool and the fluid pressure actuated spool. The unitary valve body may be comprised of the first valve body housing the operator actuated directional valve spool and a second valve body fixed to the first valve body and housing the first pressure actuated spool. The first and second valve bodies may be removably coupled to form the unitary valve body. First and second valve bodies may be removably coupled by threaded fasteners.